Alpha blocker 2605722 224001317 2008-07-06T22:03:14Z SieBot 4005189 robot Adding: [[he:חוסמי אלפא]] '''Alpha blockers''' (also called alpha-adrenergic blocking agents) constitute a variety of drugs which block [[Adrenergic receptor#Alpha .CE.B1 receptors|α<sub>1</sub>-adrenergic receptors]] in [[arteries]] and [[smooth muscle]]s. ==Indications== These drugs may be used to treat: * [[benign prostatic hyperplasia]] (BPH) **[[Lower urinary tract symptoms]] **Post [[Transurethral microwave thermotherapy]] (TUMT) and [[Transurethral needle ablation of the prostate]] (TUNA) procedures * [[high blood pressure]] (hypertension). This is not typically the drug of choice unless the patient also has BPH. * [[symptoms]] of [http://health.yahoo.com/ency/healthwise/hw72762 non inflammatory chronic pelvic pain syndrome], a type of [[prostatitis]]. As a side effect they may reduce [[blood pressure]] and result in lightheadedness. ==Examples of alpha blockers== Alpha blockers include: * [[Doxazosin]] (Cardura) * [[Prazosin]] (Minipress) * [[Phenoxybenzamine]] * [[Phentolamine]] (Regitine) * [[Tamsulosin]] (Flomaxtra/Flomax) * [[Alfuzosin]] (Uroxatral) * [[Terazosin]] (Hytrin) Tamsulosin is relatively selective for α<sub>1a</sub>-adrenergic receptors, which are mainly present in the [[prostate]]. Hence, it may have a more selective action in BPH with minimal effects on blood pressure. ==Adverse effects and interactions== By reducing α<sub>1</sub>-adrenergic activity of the blood vessels, these drugs may cause [[hypotension]] (low blood pressure) and interrupt the [[baroreflex]] response. In doing so, they may cause dizziness, lightheadedness, or fainting when rising from a lying or sitting posture (known as [[orthostatic hypotension]] or postural hypotension). For this reason, it is generally recommended that alpha blockers should be taken at bedtime. Additionally, the risk of [[first dose phenomenon]] may be reduced by starting at a low dose and [[titrate|titrating]] upwards as needed. Because these medications may cause orthostatic hypotension, as well as [[hypotension]] in general, these agents may [[drug interaction|interact]] with other medications that increase risk for [[hypotension]], such as other [[antihypertensive]]s and [[vasodilator]]s. As discussed above, tamsulosin may have less risk for hypotension and orthostatic hypotension due to its selectivity for α<sub>1a</sub>-adrenergic receptors. On the other hand, the drug (a) elevates risk for floppy iris syndrome, and (b) might show ADRs characteristic of the [[sulfa]] related drugs. ==α<sub>2</sub>-blockers== Although "alpha blocker" generally refers to α<sub>1</sub>-blockers, there are also α<sub>2</sub>-blockers, which are [[antagonists]] to the α<sub>2</sub> [[adrenergic receptor]]. Examples include [[yohimbine]], [[benzylpiperazine]], [[rauwolscine]] and [[idazoxan]]. ==References== * [http://www.drugdigest.org/DD/Comparison/NewComparison/0,10621,5-17,00.html DrugDigest] - Alpha blockers * [http://www.rxlist.com/cgi/generic2/tamsul_cp.htm RxList.com] - Tamsulosin * {{MeshName|alpha-Adrenergic+Blockers}} [[Category:Alpha blockers|*]] {{Antihypertensives_and_diuretics}} {{Urologicals}} {{Receptor agonists and antagonists}} [[de:Alphablocker]] [[es:Alfa bloqueante]] [[fr:Alpha-bloquant]] [[it:Alfa bloccante]] [[he:חוסמי אלפא]] [[ja:交感神経α受容体遮断薬]]